M92 – IMT3b Observatory

Viewing Report 10th June 2023

22:34 – 01:00

Tonight was a visual night. GingerGeek and I used the 22″ Obsession Dobsonian to view some of the wonders of the late Spring sky.

We started with Venus with the aid of a Moon filter. Whilst Venus is bright and not too overwhelming in the eyepiece, the contrast afforded by the addition of this particular filter aids the clarity of the image as Venus sits on the bright backlight of the night sky this time of year. Venus is in a gibbous phase and you could clearly see a concave arch to the edge of Venus that was missing. The seeing was very steady and we were able to push to 179x with the 13mm Nagler.

Next up was Mars. Whilst it took a while for it to appear in the astronomically twilight sky, I swept the area North East of Venus and landed the target after a few moments. Mars was so very small compared with Venus, obviously red as seen without a filter in this case and slightly shifting in colours due to the seeing. By the time we had finished looking, Mars had appeared in the night sky.

Now the sky was getting darker we wanted to start on the deep sky objects. It became apparent very quickly there was a problem with my alignment. This was a problem I faced the last time out and the trouble is with he RA encoder. The RJ11 cable has been pulled and needs recrimping. So for tonight it was about star hoping only 🙂

We then went on to look at globulars M3, M92, planetary nebulae M57 the Ring nebula and M97 the Owl nebula. We tried to get M101 but the sky brightness would not allow it. We also looked at Mizar and Alcor that I could see from 11:30pm as a double, and we looked at Polaris and it’s double star companion SAO 305 through the scope.

The planetary nebulae were seen through an OIII filter and Tele Vue Nebustar filter. I thought the view was slightly clearer through the Nebustar filter, maybe due to the slightly wider bandwidth which includes H-Beta. The Ring nebula was very crisp and I thought I could discern the central star which is 12th magnitude. Our friend Bob was kind enough to lend me a set of eyepieces he recently acquired. The Tele Vue 10mm Radian eyepiece gives 230x through which we could see the central white dwarf.

Whilst looking at the globular clusters we pushed the magnification to 288x with the 8mm Tele Vue Radian. Both this eyepiece and the 10mm gave fantastic views with the globulars sparking with pinpricks of lights from the 1,000s of Suns!

Viewing Report 1st June 2022

22:40 – 00:31

Visual this evening on the 22″ Dob. The 120 Esprit is still off the MEII so the IMT3b observatory is out of action for a few weeks whilst it is not balanced. The MyT and 120 Esprit are now packed away for the Tenerife trip which is really exciting, first time in over 2 years!

Bob came round this evening and we explored the rather bright sky given the time of year with the dob. So what what did we see?

Observing Notes

M5 seen 23:21 31mm and 13mm better than M3

M3 resolved easily 23:17 31mm and 13mm more compact than M5

M51 massive filled fov in 13mm much smaller in 31mm

M92 seen both eyepieces and very bright

M57 13mm only very large AV central star, very big ring

Viewing Report 13th June 2020 – IMT3

23:31 – 04:02

So I opened the dome late this evening as it was not due to be clear. However an opening in the cloud meant I could test guiding again on the 12″, especially whilst it was light in the late Spring weeks.

The first job was as always to focus which brought me to a reading of 61944 at 19.83℃.

Another small job was to sort the guider FoV out. I went ahead and used M92 to align the guider.

The final FoV settings are here for completness.

Set AS1600 to Gain and Offset 10 due to cluster being very bright and I needed to set a standard of 60 seconds minimum exposure. Gain 139 and Offset 21 gas saturated unless I selected 15 seconds, Gain 75 and Offset 12 saturated at 30 seconds so hence 10 and 10 which came in about 58k ADU.

I then performed a slew to a nearby star so I could centre the scope, there platsolve completed successfully and I updated TSX and the FoV for the 12″ with the new angle.

The first image of 60 seconds came down and was out of focus, I then realised changing the profile SGPro forgot the autofocus setting, so I had to stop the run, delete the images and set the original focus point then rerun.

Next I ran a few images but then to my horror I had the same guiding issue, where the star moves being dragged up and down in a periodic way. I slewed elsewhere and tried again and the problem did not occur. I was near M92 and just East of the Meridian and quite high up. Not sure why that is a problem.

I could not resolve, I waited a while then performed a meridian flip and low and behold the problem went away, again not sure why. I still have this terrible noise coming from the RA motor/gear area. I decided to bite the bullet and take off various caps on the scope listening and looking inside. I decided it was not after all, the through the mount cabling but coming from the RA gear itself, so I looked for the MEII guide for removing the worm block and then followed the instructions to take off the RA cover.

This gave me instant feedback on what the issue was, the belts driving the axis were making a noise. On looking through forums on Bisque.com I found a few people with similar issues and needing to grease the belts, they were told Lubriplate was a good grease. This is an American grease so I will find a similar here and then apply, I will ask Bob first for his suggestion.

So the night wore on and the LRGB frames of M92 I thought I would take whilst testing guiding progressed. At one point the imaging stopped due to cloud. I just caught the dome before it closed to change the safety sensor due to cloud. When it cleared it never really cleared, with the sky temperature reading about -14℃.

Nearing the end of the imaging session, I had caught about 15 frames of each of the filters.

The guider was behaving mostly with he odd funny jolt. By 3:30 am the sky was lightening very quickly.

By this time I had stopped guiding and imaging. I closed the dome, slewed the scope to the flat panel and proceeded to take a set of LRGB flats for Gain 10 Offset 0 and also Gain 139 and Offset 21 as request from the previous nights imaging.

Viewing Report 2nd June 2020 – IMT3

20:28 – 00:30

After a day of checking the mount and spending some 3 hours resetting the RA and DEC cam stop and spring plungers I have come out to see if I have resolved the image or made it worse. I can still hear the squeaking of the cables in the Through the mount position as the worm turns so I do need to remove 1 or 2 of them to free it up. However I no longer hear the knocking, tapping and grinding of the Dec axis. I am also going to capture some PEC data for Tom on the Software Bisque forum to look at. GingerGeek with his usual smoking jacket turned up to assist from a distance.

Whilst trying to find a star we came across a galaxy, NGC 5646 H126-1, which looked very interesting for the 12″, so we will come back and image that at a later date. We are in a rush for the clouds as it is to cloud over by 11:30pm. What we need to do is disable PEC, disable TPoint and Protrack and the guider relays then point at a star and guide without applying any corrections as per page 147 of the MEII manual for 15 minutes.

I went out to the dome and set with the help of GingerGeek the camera on the back of the 12″ to as close to 0 degrees as possible, in our case 0.81 degrees after plate solving.

We slewed to a start neat declination 0 and close to the Meridian on the East side of the mount called Tycho 326:747 and at 22:37 started to look at the auto-guider settings. The star was at DEC +01° 34′ 10.909″ and RA 14h 45m 20.1920. The auto-guider log in question for tonight was “Autoguider.018.log”. The star looked good in the main ZWO ASI1600mm camera which we would use to guide and collect the data. We did notice as per the image below over 15 minutes the star drifting East, so the polar alignment is out. More importantly we got the 15 minutes of data in the log as the clouds started to roll in, as can be seen in the star brightness below.

The resulting log file was read into the Sky’s PEC and the raw data shown below one we clicked ‘Fit’ on the data which scales it to this chart. The peak to peak was 0.7 arcsecs. We applied this to the mount –

Next whilst GingerGeek went off to get his beauty sleep…..he really needs it 🙂 I set about slewing to a bright star in the vicinity and calibrating the guider, since I had rotated the camera. The calibration was successful even though the RA looked slights odd as a fit. The different in the RA and Dec rate was potentially due to position on the sky and the error in the RA plotting data. I will go back and do another calibration next time it is clear.

I then slewed to M92, could not find a guide star very suitable so moved around a bit and then started to guide and see what the graph looked like. What surprised me was the the amplitude of the guiding was only 0.36 arcsecs which is really low and no guiding issues as I saw before. It looks like the adjustments to the spring plungers and cam stops may have been the cause and fix.

Guiding graph at +74 deg altitude and near M92

I performed a quick focus run whilst pausing the guiding and got 61836 and HFR 4.4 which is vert good for this scope.

Meanwhile the clouds from the North had started to drift in which was going to stop play 🙁

I managed to get a single frame and focus on M92 of 20s before the clouds stopped the guiding. So I shut up the dome, sent the logs to Software Bisque, or the chap on the forum who was kind enough to help and went off to bed.

Viewing Report 1st June 2020 – IMT3

20:25 – 00:15

Dome once again open to cool down

Solved FoV for Lodestar guider on 12″

Now guiding on star to West side of mount around 0 degrees Dec and near the Meridian to see if problem reoccurs, graph looks ok but there is a slight regular pattern of error.

Slewed to M92 which is a glob currently at Alt +74, Dec 43 and on the East side of the mount where I had issues last night. I plate solved the image.

The auto focus run looked good

Found guide star by moving M92 slightly off centre. Now guiding. All looked good for a short while. So each section of PHD2 graph is 25 points, so when you have 100 points selected there are 4 sections of the graph. This mean each section/column represents own my case 250 seconds as I expose for 10 seconds, so just over 4 minutes per section. So the errors I saw last night were about 12mins apart. This cannot be the work gear as it has a cycle of 2min 29sec. This is from the latest Paramount manual for the MEII.

Tracking at the sidereal rate, one revolution of the worm takes 149.6 seconds (2 minutes 29 seconds).
The right ascension gear has 576 teeth.
The declination gear has 475 teeth.

The error I am seeing is about 4mins. I cannot continue imaging as every few frames are trailed.